Patent Document 1 describes a configuration including a selective catalytic reduction (SCR) catalyst, an adding valve that adds urea water to exhaust gas flowing into the SCR catalyst, and a low pressure EGR (exhaust gas recirculation) system that guides a part of the exhaust gas (EGR gas) from an exhaust passage at a downstream side of the SCR catalyst to an intake passage.
Patent Document 2 describes a configuration of a spark ignition internal combustion engine including an apparatus that supplies ammonia to an intake passage and an SCR catalyst arranged in an exhaust passage.